A long film is produced by a known method such as extrusion molding and wound on a cylindrical core for storage and shipment. The film thus wound on the cylindrical core is distorted (deformed) during storage, which may cause difficulties in unwinding the film. For example, Patent Literature 1 points out such a problem.
Patent Literature 1 describes a core configured to prevent the distortion of a belt-like article resulting from the contraction of the wound article. Specifically, after the belt-like article is wound on the core in close contact with the outer periphery of the core, the core is contracted in the radial direction thereof. Then, after the core is expanded in the radial direction to increase the contact between the outer periphery of the core and the belt-like article, the belt-like article is unwound from the core.